Metal foil coatings on underlying metallic substrates are desired for many applications where the properties of the substrate in bulk are needed in combination with the surface properties of the coating. Such surface properties as color, hardness, corrosion and abrasion resistance, electrical conductivity and others can be selected by the application of a thin foil layer onto a substrate material otherwise lacking those properties.
There are many techniques available for applying coatings to substrate which run the gamut from conventional painting or adhesive approaches to more high technology processes of plasma spraying or laser surface modification. These various systems represent tradeoffs in efficiency of the coating process, adhesion of the coated layer, and the desired surface properties.
The application of laser energy has been used in the past to condition uncoated substrate surfaces such as by creating surface hardness alterations by, for example, heating of a substrate surface and creation of a pressure wave within a substrate. On the other hand, lasers have also been utilized for welding materials together by the application of sufficient energy over time to provide a thermal melting of two materials which results in a welded joint.
The need to provide surface properties which can withstand increasingly harsh treatment and environments brings forth the need to apply coatings to substrates which are not readily joined by conventional technologies such as laser welding.